Pennsylvania State Police line the streets outside St. Peters' Cathedral in Scranton, Thursday, Sept. 18, 2014, for the funeral service for slain Cpl. Bryon Dickson, 38. Photo: Reuters

The manhunt for Pennsylvania fugitive Eric Frein intensified Thursday as mourners gathered for the funeral of the state trooper he allegedly killed last week in a bizarre ambush. Schools in the area remained closed as authorities continued a three-state manhunt in pursuit of Frein and thousands of officers gathered in Scranton for Pennsylvania State Police Cpl. Bryon Dickson's funeral.

Dickson, 38, was walking to his car after his shift Friday night when someone opened fire from the woods outside the Blooming Grove barracks in rural Pike County, in the Poconos. Dickson, a former Marine, was mortally wounded. Trooper Alex Douglass was critically wounded in the attack.

Officials suspect that Frein, 31, of Canadensis, is hiding in the woods with high-powered rifles. He is considered extremely dangerous. Frein, a military re-enactment buff with anti-government and anti-police leanings, apparently shaved both sides of his head "in mental preparation to commit this cowardly act," State Police Lt. Col. George Bivens said. A federal warrant has been issued for Frein's arrest.

"In the event you are listening to this broadcast on a radio -- on a portable radio -- while cowering in some cool, damp hiding place, I want you to know one thing: Eric, we are coming for you," said Bivens.

During the funeral service attended by Gov. Tom Corbett, a flag-draped coffin was carried through the streets of Scranton in a procession led by hundreds of officers on motorcycles, according to USA Today. A marine honor guard displayed the colors and American Flag. Dickson was a seven-year veteran and had transferred to the northeastern region from the Philadelphia barracks.

Frein's sister told NBC News that he was "not a psycho." She continued: "We're not trying to protect him. He has to suffer the consequences. But he's still our family ... I don't know where he is or what he's doing. I hope it's a big misunderstanding."

Frein's father, retired Army Maj. E. Michael Frein, said two of his weapons were missing, ABC News reported. He said his son had been a member of his high school rifle team and "doesn't miss."

A Jeep believed to have been used by Frein was found Monday in a swampy area by a man walking his dog. Inside were Frein's ID and shell casings, military gear, camouflage face paint and empty rifle cases, NBC News reported.